The present disclosure generally relates to a gear set, and more particularly to a gear set that can be used for pitching, for example, a blade of a rotor of a wind turbine, a wind turbine incorporating such a gear set, and a method of servicing a wind turbine.
Wind turbines have received increased attention as an environmentally safe and relatively inexpensive alternative energy source. With this growing interest, considerable efforts have been made to develop wind turbines that are reliable and efficient.
A wind turbine typically includes a rotor comprised of a hub and a plurality of blades mounted on the hub. The blades of the rotor transform wind energy into a rotational torque or force that drives a generator. The rotor is typically coupled to the generator through a drive train, which typically includes, among other things, a gearbox. The gearbox steps up the inherently low rotational speed of the rotor for the generator to efficiently convert the rotational mechanical energy to electrical energy, which can be fed into a grid. The gearbox, the generator and other related components are typically mounted within a housing or nacelle, which is positioned on top of a truss or tubular tower.
Some wind turbines employ a pitch drive unit to change or adjust a pitch angle of each blade. The pitch angle is an angle that determines a blade's orientation about its pitch axis. In such configuration, each blade is attached to the hub through a pitch bearing which typically includes an inner race and an outer race. More specifically, the outer race is typically releasably attached to the hub, and the inner race is a ring gear that is typically releasably attached to a respective blade so that the blade is rotatable relative to its pitch axis and the hub. The pitch drive unit includes a drive gear or pinion that meshes with the ring gear, and a motor for driving the drive gear. The motor is typically supported by the hub.
In existing wind turbines, the drive gear is harder than the pitch bearing. That is, the drive gear has a hardness that is greater than the hardness of the ring gear of the pitch bearing. As a result, the ring gear is the wear component, which wears out first and needs to be replaced when the ring gear reaches its expected operational life. Replacing the ring gear typically requires detaching the rotor from the drive train and using a relatively large, land-based or vessel-based crane to lower the rotor from the top of the tower. Then on the ground, the blade is removed and the relevant pitch bearing is replaced. Relatively large cranes are needed because the rotors can be very large and heavy—wind turbines designed to provide electricity to a utility grid, for example, can have rotors of 30 or more meters in diameter. This approach is time-consuming, relatively complicated and expensive.
Accordingly, it would be desirable to provide a gear set, a wind turbine incorporating such a gear set and a method of servicing a wind turbine, which address at least some of the problems identified above.